1. Field of the Invention
This invention relates to control of incompetent subterranean formations penetrated by wellbores.
2. Brief Description of Prior Art
In the production of fluids, such as oil, gas, water, and the like from subterranean formations, a number of difficulties are encountered when the well through which the fluids are produced penetrates an incompetent or unconsolidated subterranean formation. Such formations frequently are composed of incompetent sand, and grains of the sand become entrained in the fluid being produced and are carried into the wellbore. The result of such entrainment, among other things, is often the abrasion of the pumping equipment in the wellbore, clogging of the strainers, sand bridging in tubing, plugging of surface flow lines, filling of oil-water separators and the sanding in of a cavity immediately adjacent to the strainers. These effects, in turn, ultimately cause a sharp decrease in the rate of production of hydrocarbon fluids and increase maintenance costs.
Various solutions to this problem have been proposed. For example, gravel and sand packs employing the injection of particulate solids in thickened hydrocarbons wherein the thickening agent is an aluminum soap of fatty acids, finely-divided silica, bentonite, certain other soaps (NAPALM) and the like have been employed as are disclosed by exemplary patents (U.S. Pat. Nos. 2,906,338, 2,978,024, 3,498,380, and 3,064,730).
One of the more successful solutions to the problem of incompetent formations has been the use of thermosetting polymeric resins for injecting into the wellbore in combination with solid particulate matter to form a consolidated zone adjacent to the wellbore in the sand-producing zone. Such techniques are shown in U.S. Pat. Nos. 3,378,071, patented Apr. 16, 1968, by Derry D. Sparlin and assigned to Continental Oil Company as well as 3,692,116 by Derry D. Sparlin and assigned to Continental Oil Company. U.S. Pat. Nos. 3,378,071 and 3,692,116 are hereby incorporated by reference.
Gelled water systems are presently used for placing the gravel and plastic against subterranean formations for controlling incompetent sand. However, it is desirable in many instances to use a gelled oil system in many formations wherein the oil is more compatible with the subterranean environment than water. Water in some formations impairs the production of fluids from the well by forming emulsions within the oil in the formation, hydrating shales or clays in the formation, and the like. An oil base system prevents these problems and is diluted by the produced crude oil which facilitates the initial production of oil from the well after well treatment.
A further patent relating to a similar process is U.S. Pat. No. 3,391,738, patented July 9, 1968, by Derry D. Sparlin and assigned to Continental Oil Company. U.S. Pat. No. 3,391,738 is hereby incorporated by reference.
In such processes, the mixture injected into the formation to consolidate the portions of the subterranean formations surrounding the wellbore comprises a polymeric resin which polymerizes in situ and, in many instances, contains particulate material. In the use of such processes, it has long been considered desirable that a gelled oil, or the like, be available for suspending the sand and unpolymerized resins during injection into the wellbore. Such a gelled oil wherein a base-settable thermosetting resin is employed has been unavailable to the art heretofore since gelling agents useful to gel light hydrocarbons have been found to be incompatible with the base-settable thermosetting resins injected. As a result, the art has used naturally viscous oils and the like to suspend the particulate matter with the polymeric resins.
The use of viscous oils and the like results in difficulty in removing the viscous oil from the formations once the resins have polymerized. Accordingly, considerable time has been devoted to attempt a development of gelled oil mixtures which are capable of suspending the particulate matter for injection into the wellbore in combination with the polymeric resins without adversely affecting the performance of the resins.